The first discovery of larval Gnathostoma hispidum (Nematoda: Gnathostomidae) from a snake host, Agkistrodon brevicaudus

The present study was performed to observe the infection status of several kind of animals with indigenous Gnathostoma in Korea, and morphological characteristics of gnathostome larvae detected from pit-viper, Agkistrodon brevicaudus, for the species identification. To know the existence of Gnathostoma in Korea, 3,450 loaches, 24 bullfrogs, several kinds of snakes, i.e., 55 Elaphe rufodorsata, 2 Dinodon rufozonatum rufozonatum, 62 Rhabdophis tigrinus tigrinus and 87 Agkistrodon spp., and 438 cats were examined. A total of 21 larval gnathostomes was detected from 12 pit-vipers, A. brevicaudus. They were 2,233 x 0.343 mm in average size and covered with about 210 transverse rows of minute cuticular spines. Their characteristic head bulbs were provided with 4 rows of hooklets of which average numbers in each row were 36.8, 39.0, 41.7 and 44.3, posteriorly. In the cross sections of midgut level, the intestinal wall consisted of a single layer of 19-25 elongate epithelial cells with a single nucleus. SEM observation of the larvae revealed unique features of head bulb, cuticular spines on transverse striations and a cervical papilla. On the basis of above morphological characteristics, they were identified as the advanced third-stage larvae of Gnathostoma hispidum. It was first confirmed that the pit-viper, Agkistrodon brevicaudus is the snake intermediate host of G. hispidum.